According to the official twitter, the final episode of Bakemonogatari
will be streamed today (i.e. June 25th JST) in the official website
. It was scheduled to be aired in the mid-June.
Source: Bakemonogatari official twitter
The streaming of the final episode started at 11:55pm.
Bakemonogatari streaming site pretty heavy as expected
According to the official blog, the OP animation will be completed next week. Meanwhile, a live action version of the OP will be aired instead.
Source: Bake official blog